package day07;
/**
 * 需求：生成?位验证码(大写字母，小写字母，数字)
 */

import java.util.Random;

public class VerificationCode {
    public static void main(String[] args) {
        String code = generateVeriCode(4);
        System.out.println("验证码:"+code);
    }
    /** 生成验证码 */
    public static String generateVeriCode(int len){
        String code = "";
        char[]chs ={'a','b','c','d','e','f','g','h','i','j','k',
                'l','m','n','o','p','q','r', 's','t','u','v','w',
                'x','y','z','A','B','C','D','E','F','G','H','I',
                'J','K', 'L','M','N','O','P','Q','R','S','T','U',
                'V','W','X','Y','Z','0','1','2','3', '4','5','6','7','8','9'};
        Random rand = new Random();//2)        语句  1==语句(2+2)
        for (int i=1;i<=len;i++){//len次
//            int index = (int)(Math.random()*chs.length);1)
            int index =rand.nextInt(chs.length);//2)  随机下标
            code +=chs[index];//获取随机字符并拼接到code中
        }
        /*
        i=1  index=0  code="a"
        i=2  index=1  code="a9"
        i=3  index=2  code="a9z"
        i=4  index=3  code="a9zC"
        i=5  false
         */
        return code;
    }
}
